Add a full keyboard shortcut system and a shortcuts cheatsheet to the web chat

Category: Chat / Web app

Description:

The web chat currently only documents two shortcuts: Enter to submit and Cmd/Ctrl+Enter to submit. Everything else — starting a new chat, switching models, toggling the sidebar, stopping a generation, copying a response, opening settings — requires the mouse. For anyone who uses Venice as a daily driver (especially with long prompts and multi-model workflows), this is the biggest remaining friction in the UI.

Proposed shortcuts (macOS uses Cmd, Windows/Linux uses Ctrl):

Action	Shortcut
Command palette (search chats, models, settings, actions)	Cmd/Ctrl + K
New chat	Cmd/Ctrl + Shift + O
Toggle sidebar	Cmd/Ctrl + B
Focus the prompt input	/ (when not already typing) or Cmd/Ctrl + J
Model picker	Cmd/Ctrl + Shift + M
Stop / cancel current generation	Esc
Regenerate last response	Cmd/Ctrl + Shift + R
Edit last user message	Up arrow in empty input
Copy last response as markdown	Cmd/Ctrl + Shift + C
Toggle temporary/incognito chat	Cmd/Ctrl + Shift + N
Show shortcuts cheatsheet	? or Cmd/Ctrl + /
Previous / next chat in history	Alt + Up / Alt + Down
Attach file	Cmd/Ctrl + U

Implementation notes:

Keep Enter = submit and Shift+Enter = newline as they are; do not break muscle memory.
Shortcuts should be disabled while the user is typing in a text field, except for the explicit submit/stop ones.
Ideally expose a small "Keyboard shortcuts" entry in Settings that lists them and allows rebinding later.
A ? overlay is a cheap first step and makes the feature discoverable without a docs page.

Why it matters: power users, developers, and anyone on a laptop without a mouse. It also makes the web app feel consistent with other AI chat tools that already ship these.

Alternatives considered: browser-level shortcuts and bookmarklets, but they cannot reach internal app actions like model switching or sidebar state.